The present invention relates to a moving image compression/decompression apparatus and method, and particularly to a moving image compression/decompression apparatus and method which use a wavelet transform technique so as to improve a compression rate.
In recent years, there has been much transmission service of image data or audio data over the internet. Also, in the field of security system, there has been much research on a realtime transmission of stored data as well as data storage.
For this, methods for increasing a transmission rate of a network or transmitting compressed data are proposed. However, in the former method, a transmission rate of a network can not be increased to more than some extent. Moreover, since the transmission rate becomes decreased even in the high speed network when users connected to the network increase, enormous costs and expenses are consumed without remarkable effect. In the latter method, there are various standardized compression methods such as MJPEG (Motion JPEG), MPEG-1, MPEG-2, MPEG-4, or the like. Video on demand (VOD) or realtime service are performed using the compression methods and buffering method. VOD service is not performed in realtime since it uses compressed and pre-stored data, and realtime service performed using the buffering method has problems about system workability and stability when processing is delayed on the reception side, or the transmission rate of the network decreases.
It is an object of the present invention to provide a moving image compression/decompression apparatus and method for compressing moving image data in high compression rate and transmitting them in realtime through the practical network.
According to a first aspect of the present invention, there is provided a moving image compression/decompression apparatus comprising a A/D converter for converting moving image data into digital data, a wavelet transformer for dividing the digital data converted by the AID converter into a plurality of level regions and wavelet-transforming the divided data, a quantizer for quantizing the data wavelet-transformed by the wavelet transformer with predetermined weight corresponding to each of the level regions, a SZT coder for performing a lossless OPCM coding with respect to the data quantized by the quantizer sequentially from high level region to low level region using a similarity between the level regions based on a predetermined SZT map, a Huffman coder for encoding the data subject to SZT coding by the SZT coder based on the probability of high frequency components which exist in each of the level regions, and a stream file generator for outputting the data encoded by the Huffman coder as bit stream.
According to a second aspect of the present invention, there is provided a moving image compression/decompression method comprising the steps of (a) converting moving image data into digital data, (b) dividing the digital data converted in the stop (a) into a plurality of level regions and wavelet-transforming the divided data, (c) a quantizer for quantizing the data wavelet-transformed in the step (b) with predetermined weight corresponding to each of the level regions, (d) performing a lossless DPCM coding with respect to the data quantized in the step (c) sequentially from high level region to low level region using a similarity between the level regions based on a predetermined SZT map, (e) encoding the data subject to SZT coding in the step (d) based on the probability of high frequency components which exist in each of the level regions, and (f) outputting the data encoded in the step (a) as bit stream.